The attack button must be pressed again at the moment that the previous hit connects with the target, and must only be pressed once for each attack. Each attack resulting from a correctly timed press will result in a Critical Strike.

Note that it also benefits each strike in the the sword flurry attack after a Wraith Stun (which can build the Hit Counter extremely quickly), and also applies to Throwing Daggers (pressing the dagger throw button again the moment the previous dagger strikes the target). Likewise, Counter and Ground Finisher moves can also chain from, and be chained into, a Critical Strike on the subsequent attack.